Electric discharge apparatus



June 13, 1939. SMEDE 2,162,519

ELECTRIC DISCHARGE APPARATUS Original Filed May 3, 1953 2 Sheets-Sheet l June 13, 1939. L. SMEDE 2,162,519

ELECTRIC DISCHARGE APPARATUS Original Filed May 3, 1933 2 Sheets-Sheet 2 /2/ 9 L Load izyfi.

WITNESSES: INVENTOR I Lioyd Swede.

T'TORNEY Patented June 13, 1939 UNITED STATES PATENT OFFICE Lloyd Smede, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa.,

sylvania a corporation of Penn- Original application May 3, 1933, Serial No. 669,273, now Patent No. 2,008,730, dated July Divided and this application May 23,

1935, Serial No. 22,996

3 Claims.

My invention relates to electric discharge apparatus and has particular relation to apparatus for producing impulses such as are utilized for providing starting currents and starting poten- 5 tials for vapor discharge devices.

The present application is a division of my copending application Serial No. 669,273, filed May 3, 1933, patent No. 2,008,430, dated July 23, 1935.

It is an object of my invention to provide a simple system for producing peaked current or potential impulses.

Another object of my invention is to provide a system for producing peaked impulses, the magnitude and duration of which shall be capable of variation with facility.

A further object of my invention is to provide impulses for starting vapor discharge devices which shall be capable of precise timing, thus making possible the precise starting of the discharge devices.

More concisely stated, it is an object of my invention to provide apparatus for producing impulses of whatever magnitude may be desired, but of such short duration that regardless of the magnitude of the impulses the conductors through which the impulses are transmitted are not deleteriously affected.

According to my invention, I provide apparatus incorporating an electric discharge device of the gas-filled type. The discharge device is preferably provided with a control electrode and a plurality of principal electrodes. A capacitor is connected between the principal electrodes and charging means is provided for the capacitor which is capable of charging it to such a potential that the discharge device becomes energized at the desired instant. By properly adjusting the potential applied to the control electrode the point at which the discharge device becomes energized and consequently the interval of time during which the capacitor is charged to produce the excitation of the discharge device may be regulated.

' The discharge device is in the specific embodiment of my invention which shall be described herein as a rectifier of the type having a control electrode. My invention, of course. is not to be limited to apparatus incorporating only rectifiers. since it is equally as well applicable to a discharge device of the symmetric type.

In the following discussion the potential impressed between the control electrode and the cathode of the rectifier shall be designated as the control potential. The potential impressed between the anode and the cathode of the rectifier shall be designated as the principal potential of the rectifier and the cathode shall be taken as the reference point of potential. Moreover, the control potential at any principal potential above which the rectifier is just energized and below which it remains deenergized shall be designated as the limiting control potential.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood when read in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic view showing a preferred embodiment of my invention;

Figs. 2 and 3 are graphs illustrating the operation of Fig. 1;

Fig. 4 is a diagrammatic view showing a modification of my invention; and,

Fig. 5 is a graph illustrating the operation of a system such as is shown in Fig. 4.

Specifically my invention is described herein as applied to the starting of a discharge device of the Ignitron tube type. It is obvious that my invention may be utilized for starting discharge devices of all types and the specific embodiment described herein is not to be taken in any manner as limiting the scope of my invention.

The apparatus shown in Fig. 1 comprises an electric discharge device I having an anode 3, preferably of a material such as nickel or carbon. and a cathode 5. preferably of mercury. disposed in a chamber 1 that is preferably highly evacuated. A starting electrode 9 is immersed in the mercury 5.

The electric discharge device I is supplied with potential from a suitable power source (not shown) through a transformer l5. one section I! of the secondary IQ of which is connected between the anode 3 and the cathode 5 thereof throu h a load 2| of any general character that might be energized through the electric discharge device.

The starting potential for the electric discharge device is provided by a capacitor 23 that is periodically charged from another section 25 of the secondary l9 through a rectifier 21 and is discharged through another rectifier 29 of the grid controlled type. The anode 3| of the grid controlled rectifier 29 is connected to one plate 33 of the capacitor 23 while the cathode 35 is connected to the starting electrode 9 of the electric discharge device I through a resistor 31 of suitable character. The other plate 33 of the capacitor 23 is connected to the mercury cathode 5 of the electric discharge device I. The network 4| comprising the capacitor 23, the principal circuit of the grid controlled rectifier 29, the resistor 31, the starting electrode 9 and its cooperative mercury electrode 5 has a predetermined time constant depending on the magnitudes of the various elements. By varying the resistor 31 in series with the grid controlled rectifier 29 the time constant of the network 4| may be varied. The time constant of the network 4| determines the rate at which the capacitor when charged is discharged through the network, and consequently determines when the principal current in the electric discharge device I will be initiated.

The resistor 31 is utilized in the discharging network 4|, by reason of the fact that the start ing current must be supplied for at least a small interval of time before the discharge between the principal electrodes 3 and 5 is initiated. If the starting current does not persist for at least this interval of time the electric discharge device fails to become energized in spite of the magnitude of the starting current. The time constant of the starting network 4| is of such magnitude that the starting current persists for the neces sary interval of time. The time interval is of course extremely small and in practice varies from O to 500 micro-seconds.

The capacitor 23 is connected in series with the rectifier 27 through which it is charged and with a resistor 43 of suitable character. The cathode 45 of the rectifier 2"! is connected to the plate 33 of the capacitor 23 to which the anode 3| of the grid controlled rectifier 29 is connected and the anode 41 of the rectifier is connected to one terminal 49 of the section of the secondary |9 whereby the capacitor 23 is charged. The network 5| including the section 25 of the secondary I!) through which the capacitor 23 is charged, the rectifier 2'! through which it is charged, the capacitor 23 and the resistor 43, have a predetermined time constant which, in turn, determines the rate at which the capacitor 23 is charged.

The section 25 of the secondary |9 through which the capacitor 23 is charged is so wound that the potential impressed across the network is in opposite phase relationship to the principal potential impressed on the electric discharge device and the potential impressed on the terminal 49 to which the anode 41 of the rectifier 2'! is connected is 180 out of phase with the potential impressed on the terminal 53 to which the anode 3 of the electric discharge device is connected. Consequently when the potential of the anode 3 of the electric discharge device I is negative relative to the potential of the mercury cathode 5, the anode M of the rectifier 21 through which the capacitor 23 is charged is positive relative to its cathode 45, and current is transmitted through the rectifier 21 to charge the capacitor. It will be seen that as long as the anode 3 of the electric discharge device I is negative the device remains deenergized. During this interval the capacitor 23 is charged through the rectifier 21. In practice the resistor 43 in the charging network 5| is of such magnitudethat the capacitor 23 is charged during a comparatively small fraction of the half cycle of positive potential applied to the charging network 5|.

The control electrode 55 of the grid controlled rectifier 29 is connected to the anode 3 of the electric discharge device I through a portion of the windings of a potentiometer 51, a suitable resistor 59 and the load 2|. The potentiometer 51 is energized from a battery 60 and the potential of the control electrode 55 is in the preferred practice of my invention maintained negative relative to the cathode of the rectifier 29. By thus maintaining the control potential of the rectifier 29 negative the rectifier is maintained deenergized during any desired fraction of the half cycles of principal potential that are impressed on the electric discharge device I. It is to be noted that during the negative half cycle of principal potential of the electric discharge device I, the control potential of the grid controlled rectifier is negative by reason of the fact that negative potential is supplied by the secondary section I! of the transformer IS. The negative potential thus supplied is superimposed on the negative potential provided by the potentiometer 51 and the sum of these two negative potentials is, in general, sufficient to make certain that the grid controlled rectifier 29 is deener-t gized during the interval during which the negative half wave of principal potential is impressed on the electric discharge device I. However, when the positive half wave of principal potential is impressed on the electric discharge device I, the potential impressed by the secondary section I! between the control electrode 55 and the oathode 35 of the grid controlled rectifier 29 becomes increasingly positive and the negative potential provided by the potentiometer 51 is decreased until such a value of control potential is attained that the rectifier 29 becomes energized. It is to be observed that since in practice the grid controlled rectifier 29 is preferably of the gas-filled type it passes abruptly from a deenergized condition to a fully energized condition.

The grid controlled rectifier 29 is thus energized after the capacitor 23 has been charged and the charge on the capacitor is transmitted therethrough and through the starting electrode 9 and the mercury electrode 5. By reason of the transmission of the current through the starting electrode 9 a discharge is initiated in the electric discharge device I and persists substantially until the half cycle of principal potential passes through a zero value and becomes negative.

The operation of the system is illustrated. in Figs. 2 and 3. The positive half wave of principal potential is represented by the upper full line curve 6| in each graph. The potential to which the capacitor 23 is charged through the rectifier 2'! associated therewith is represented by the horizontal line 63 that is parallel to the axis of abscissa 65 in each graph. The control potentials at which the grid controlled rectifier 29 becomes energized for values of principal potential corresponding to the principal potential of the electric discharge device I lie on the lower full line curve 61 which has a slope of polarity opposite to the polarity of the slope of the principal potential curve 6|. In accordance with the foregoing nomenclature the curve 61 may be designated as the limiting control potential curve. The limiting control potential corresponding to the potential impressed on the capacitor is represented by a straight line 69 parallel to the axis of abscissa 65 and intersecting the limiting control potential curve 61 at the point N that corresponds to the potential impressed on the capacitor 23. The line 69 may be regarded as the limiting control potential curve for the grid controlled rectifier when the capacitor is charged to a value represented by the upper horizontal line 63. The negative control potential that is normally impressed between the control electrode 55 and the cathode 35 of the rectifier 29 by the potentiometer 51 is represented by the lower horizontal line 13 in each plot.

When a positive half wave of principal potential is impressed on the electric discharge device I the control potential impressed on the grid control rectifier 29 is represented by the broken line curve 15 which, it will be noted, is simply the upper full line curve 6| representing the principal potential impressed on the electric discharge device I added to the lower horizontal line 13 representing the negative control potential provided by the potentiometer 51. The grid controlled rectifier 29, and consequently the electric discharge device I, are energized approximately at a point corresponding to the point 11 of intersection of the broken line curve I5 and the horizontal line 69 representing the limiting control potential for the grid controlled rectifier 29. The electric discharge device I then remains an ergized during the remaining portion of the positive half cycle. The interval during which the electric discharge device I remains energized is represented by the shaded region 19 under the principal potential curve BI.

The graphs shown in Figs. 2 and 3 correspond to two different values of negative control potential provided by the potentiometer 51. As can be seen in the system represented by the curve shown in Fig. 3, the negative control potential is greater than in the system represented in Fig. 2, and consequently, the electric discharge device I is energized later in the cycle in system such as is represented in Fig. 3 than it is in a system such as is represented in Fig.

Attention is called to the fact that with a system such as is shown in Fig. l. the output of the electric discharge device can only be controlled for the first half of the half cycle of positive principal potential. The limiting condition is represented by a situation in which the potentials are of such value that the broken line curve I5 is tangent to the straight line 69 representing the limiting control potential of the grid controlled rectifier 29.

To attain control during the complete half cycle of principal positive potential a system such as is shown in Fig. 4 is provided. In this system the phase of the potential impressed between the control electrode 55 and the cathode 35 of the grid controlled rectifier 29 is shifted relative to the principal potential of the electric discharge device I and by the shifting of the phase the control during any portion of the half cycle of positive principal potential impressed on the electric discharge device is provided.

In the system shown in 4 the charging network 5| for the capacitor 23, the discharging network II for the capacitor and the other circuits associated with the electric discharge device I are substantially the same as the correspondlng networks and circuit of the system shown in Fig. 1. However, the control circuit for the grid controlled rectifier 29 is radically different from the corresponding circuit of the system shown in Fig. 1.

An additional section 83 of the secondary I9 of the power supply transformer I5 is provided. The center tap 85 of the secondary section 83 is connected to the anode 3I of the grid controlled rectifier 29 through a suitable resistor 81. The terminal taps 99 and 9| of the section 83 are connected to the terminals of a phase-shifting network 93 comprising a variable resistor 95 and a capacitor 91 connected in series with each other. The junction point 99 of the resistor 95 and the capacitor 91 is connected to the control electrode 55 of the grid controlled rectifier 29 through the potentiometer 51 of the type utilized in the system shown in Fig. 1.

It is to be noted that the phase of the potential of the junction point 99 of the resistor 95 and the capacitor 91 relative to the potential impressed between the terminal taps 89 and 9| of the secondary section 83 may vary from zero to 180 as the magnitude of the resistor 95 is varied and correspondingly the phase of the potential impressed between the control electrode 55 and the other electrodes 3| and 35 for the grid controlled rectifier 29 is varied relative to the other potentials in the system in the same manner.

The phase-shifting section 83 of the secondary I9 may be wound in the same manner as the section I! of the secondary I9 whereby principal potential is supplied to the electric discharge device I. Consequently, by varying the resistor in the phase-shifting network of the system, the phase of the control potential may be shifted relative to the principal potential through an angle of 180. The operation of the system is illustrated in Fig. 5 in which the principal potential of the electric discharge device I, the principal potential of the rectifier, the limiting control potentials of the grid controlled rectifier 29 and the negative control potential impressed on the grid controlled rectifier 29 are represented in the same manner as the corresponding elements of the system shown in Fig. 1 are represented in Figs. 2 and 3. The control potential is represented by a broken line sine curve IOI built up on the horizontal line I3 representing the negative control potential. As can be seen the broken line curve IOI intersects the limiting control potential curve 69 at a point I03 which as far as its time coordinate is concerned lies in the latter half of the positive half cycle of principal potential impressed on the electric discharge device. The electric discharge device I is, therefore, energized at this point and remains energized during an interval represented by the shaded area 19 under the principal potential curve 66.

In the system of the type shown in Fig. 1 that I have found particularly useful, the electric discharge device I is of the type substantially as shown in Fig. l and incorporates a mercury cathode 5, a nickel anode 3, and a starting electrode 9 of boron and boron carbide mixture of which the resistivity is at least .04 ohm per cubic inch and which has an heterogeneous string structure. The output potential of the section 25 of the secondary I9 whereby the capacitor 23 is charged is of the order of several hundred volts. The rectifier 21 through which the capacitor 23 is charged is of the gas filled type and is known as the Westinghouse KI626. The capacitor 23 may vary from .1 microfarad to 16 microfarads, depending on the condition of the starting electrode 9. The grid controlled rectifier 29 is of the type known as the Westinghouse KU-628. The resistor 31 in the discharging network 4| of the capacitor 23 may vary from 2 to 10 ohms. The resistor 59 in series with the control electrode 55 of the grid controlled rectifier 29 and the potentiometer 51 associated therewith is of the order of 25,000 ohms. The principal potential impressed on the electric discharge device I is of the order of volts.

Finally it is to be noted that in certain applications of-my invention'the rectifier Z! in the :charging network 5| may be omitted. While in certain connections I have found that the rectiher 21 may be omitted in apparatus in which the starting potential is applied in opposite phase to the principal potential of the electric discharge .device I, the charging network without the recthe positive half cycle of principal potential.

During the negative half cycle of principal potential the capacitor 23 is charged negatively and the following half cycle of positive principal po tential is discharged and recharged positively through the windings of the secondary section 25 whereby the charging potential is supplied.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination, a capacitor, an electric discharge device having a plurality of principal electrodes between which. a discharge is to pass, and an electrode for cntrolling said discharge, said discharge device being of the type which passes abruptly from a deenergized condition, in which discharge is not transmitted between its electrodes, to an energized condition, in which a discharge is transmitted, a first periodic potential source for impressing potentials between said control electrode and one of said principal elec trodes, means for coupling said capacitor b tween the principal electrodes of said discharge device whereby when said capacitor is charged a potential resulting from the charge on said ca 'pacitor is impressed between said electrodes, and means including a second periodic potential source of the same frequency as said first source, for charging said capacitor to a potential such that said discharge device passes from a deenergized to an energized condition, the potentials supplied by said first and second sources being in opposite phase relationship.

2. In combination, a capacitor, an electric dis-- charge device having a plurality of principal electrodes between which a discharge is to pass, and an electrode for controlling said discharge, said discharge device being of the type which passes abruptly from a deenergized condition, in which a discharge is not transmitted between its electrodes, to an energized condition, in which a discharge is transmitted, means for so coupling said capacitor between the principal electrodes of said discharge device that, when said capacitor is charged, a potential resulting from the charge on said capacitor is impressed between said principal electrodes and when said discharge device is energized a substantial portion of the discharge current is supplied by the charge on said capacitor, means for charging said capacitor to a potential such that said discharge device passes from a deenergized to an energized condition, means independent of said capacitor [or impressing a direct-current potential between said control electrode and one of said principal electrodes, the last said means including means for varying the magnitude of said direct-current potential thereby to vary the magnitude of the potential difference which is impressed on said capacitor to produce a transition from a deenergized to an energized condition, said charging means for the capacitor including an alternating source, and

means for superimposing a substantially con-,

stant .alternating potential on the direct-current potential which is of variable phase relation to the alternating potential included in the charging means.

3. In combination, a capacitor, an electric discharge device having a plurality of principal electrodes between which a discharge is to pass, and an electrode for controlling said discharge, said discharge device being of the type which passes abruptly from a deenergized condition, in which I a discharge is not transmitted between its electrodes, to an energized condition, in which a discharge is transmitted, means for so coupling said capacitor between the principal electrodes of said discharge device that when said capacitor is charged a potential resulting from the charge on said capacitor is impressed between said principal elctrodes and when said discharge device is energized a substantial portion of the discharge current is supplied by the charge on said capacitor, means including a source of alternating potential for charging said capacitor to a potential such that said discharge device passes from a deenergized to an energized condition, and means for impressing a potental betwen said control; electrode and one of said principal electrodes that includes at least an alternating component, the last said means including means for shifting the phase of said alternating component relative to the alternating potential of the source included in said charging means.

LLOYD SMEDE. 

